Observe the stomach bottom section of the specimen (H.E staining)

Visually, the mucosa is purple-blue, followed by light red submucosa, red muscularis and lightly pigmented adventitia.

At low magnification, the stomach wall is divided into four layers from the inside out.

(1) Mucosa: It is divided into three layers from the inside out.

① Epithelium: It is a single columnar epithelium. Epithelium sags downward to form gastric pits. The nucleus of columnar cells is located at the base, the cytoplasm at the top is full of transparent areas, mucin particles are lightly stained, and the boundaries between cells are clear. Tubular structures similar to columnar cells are common in connective tissue on the surface of deep epithelium, which is the cross section of nearby gastric pits.

② lamina propria: connective tissue, including blood vessels, lymphoid tissue, scattered smooth muscle cells and a large number of gastric fundus glands. The fundus gland is located between the gastric pit and the mucosal muscle. It is a single tubular gland with a small cavity and is not easy to see. It is mainly composed of parietal cells and main cells.

③ Mucosal muscle layer: thin, consisting of two layers of smooth muscle outside the inner ring.

(2) Submucous layer: loose connective tissue, containing large blood vessels, lymphatic vessels and submucosal nerve plexus, consisting of several nerve cells and unmyelinated nerve fibers. You can see (3) Muscular layer: thick, composed of smooth muscle of inner diagonal line, middle ring and longitudinal outer line.

(4) adventitia: serosa, which consists of loose connective tissue and mesothelium on the outer surface. At high magnification, the gastric fundus gland consists of five kinds of gland cells, mainly parietal cells and main cells.

(1) parietal cells: There are many cells in the neck and body of the gastric fundus gland, which are round or triangular in size, with round nuclei, often binuclear, and live in the center of the cells. The cytoplasm is red.

(2) Main cells: numerous, especially in the glands and bottom of the stomach. The cells are columnar, with round nuclei and located at the base. The cytoplasm is blue, and the small vacuole zymogen particles at the top of the cell dissolve.

(3) Neck mucus cells: few in number, located in the neck. Cells are columnar or cup-shaped. The nucleus is oblate or triangular and located at the base. The cytoplasm is full of mucin granules.

(4) Endocrine cells and stem cells are difficult to distinguish on H.E staining specimens.

The stomach is located under the diaphragm and above the abdominal cavity. Chinese medicine divides the stomach into three parts: upper, middle and lower. The upper part of the stomach is called epigastrium, including cardia; The middle part is called zhongwan, which is the body of the stomach; The lower part is called inferior epigastrium, including pylorus. The main physiological function of the stomach is to receive and decompose Shui Gu, which is contrary to the spleen.

The stomach wall has four layers: (1) mucosa, which can be divided into epithelium (single columnar epithelium with mucous cells on its surface), lamina propria (gastric fundus gland, stoma gland and pyloric gland) and muscularis mucosa (2); Submucous layer (connective tissue) (3) Mucosal muscle layer has thick smooth muscle (composed of three layers of smooth muscle: inner oblique ring and outer longitudinal ring) (4) The outer membrane is serosa.

The fine structure of the stomach wall is introduced as follows:

The stomach wall is composed of mucosa, submucosa, muscularis and adventitia, with nerves, blood vessels and lymphatic vessels.

1. Mucosal mucosa is soft and orange in the body. When the stomach is empty, it forms many folds, and when it is full, it becomes flat. The mucosa at the pylorus forms an annular fold and protrudes into the cavity, which is called pyloric valve. Gastric mucosa can be divided into three layers.

(1) Epithelium: Single-layer columnar epithelium, neatly arranged, which can secrete mucus to cover the surface of gastric mucosa and prevent gastric acid and pepsin from damaging gastric mucosa.

(2) lamina propria: It is composed of connective tissue and contains a large number of gastric glands, namely, cardia gland, pyloric gland and fundus gland. The cardia gland and pyloric gland are located in the lamina propria of cardia and pylorus respectively, and mainly secrete mucus. The fundus gland is mainly located in the fundus and lamina propria of the stomach body, and is the main gland that produces gastric juice. The gastric fundus gland is composed of many kinds of gland cells, mainly main cells and parietal cells.

Mucosal epithelium sags downward to form a tubular gastric gland, which consists of the following parts:

Main cells, also known as gastric enzyme cells, are abundant and mainly distributed in the middle and lower part of the gastric fundus. The cell body is cylindrical, the nucleus is round, the cytoplasm is basophilic and there are zymogen particles. Its main function is to secrete pepsinogen.

Parietal cells, also known as hydrochloric acid cells, are mainly distributed in the upper half of gastric fundus gland. The cells are large, triangular or round, with eosinophilic cytoplasm and red he staining. The main function of parietal cells is to secrete hydrochloric acid, which can activate pepsinogen and kill bacteria. At the same time, parietal cells also secrete endogenous factors, which can promote the absorption of vitamin B 12.

There are few cervical mucus neck cells, which are distributed in the upper part of gastric fundus gland and sandwiched between parietal cells. Cells are columnar, with oblate nuclei, located at the base of cells, which are filled with mucin particles and can secrete mucus.

In addition, there are undifferentiated cells and endocrine cells in the gastric fundus gland.

(3) Mucosal muscle layer: it is a thin layer of smooth muscle, which is longitudinally arranged in the inner ring, which is beneficial to the discharge of gastric gland secretions.

2. The submucosa is composed of loose connective tissue, including lymphocytes, mast cells, nerve plexus, blood vessels and lymphatic vessels.

3. The muscular layer of stomach is developed, which consists of three layers of smooth muscle: medial oblique muscle, middle ring muscle and lateral longitudinal muscle. Among them, the annular smooth muscle in the middle layer thickens at the pylorus to form pyloric sphincter, which has the function of controlling the discharge of gastric contents.

4. The adventitia is serosa, which consists of mesothelium and a small amount of connective tissue.

Why does the stomach not digest itself?

After eating food, people are quickly digested by gastric juice. Gastric juice is very sour, but it never digests itself. What is the secret?

In fact, while digesting food, gastric juice also does some damage to the stomach wall, which leads to the death of some cells. However, due to the strong regenerative ability of the stomach, this damage is only temporary, and the stomach can recover quickly. According to the research data of Professor Deben from the Department of Medicine, University of Michigan, the stomach surface can produce about 500,000 new cells every minute. In other words, it only takes three days to regenerate a new stomach. However, because gastric juice can dissolve gastric tissue in a few hours, it is too late to completely compensate for the loss caused by the new cells. Therefore, you have to have another skill.

The second ability of the stomach is that the stomach wall is covered with a thick layer of epithelial cells called gastric mucosa. It is in direct contact with gastric juice, so that corrosive gastric juice cannot penetrate into the inner wall of the stomach. We know that if too much acid is produced in the stomach, it will lead to gastric ulcer. Because gastric mucosa has a special protective effect, it can be protected from or only slightly eroded by acid.

Gastric juice is mainly composed of pepsin and hydrochloric acid. Pepsin is a protein and a harmless digestive enzyme. But hydrochloric acid is different. It is very corrosive and easily destroys the tissues and cells of the stomach. Therefore, it is not enough to rely only on the regenerative ability of the stomach and the protective effect of the gastric mucosa. Epithelial cells in the stomach wall are covered with a thin layer of carbohydrates, the so-called sugar body layer. Can further strengthen the protection of the stomach. In addition, the inner layer of the stomach wall is covered with a layer of fatty substances called lipids. This substance has a strong blocking effect on hydrogen ions and chloride ions of hydrochloric acid, which is the third trick for the stomach to protect itself.